Ever since silica-based optical fibers have been used for high-power lasers and amplifiers, there have been ongoing efforts to increase the power of the signal that is transmitted through the fibers, and also to improve energy efficiency during signal amplification.
In conventional laser pumping, energy is transferred from an external source to a gain-doped fiber (or other laser gain medium). That transferred energy is absorbed in the fiber, thereby producing excited states in the atoms within the fiber. At a given point, the number of particles in one excited state exceeds the number of particles in the ground state (or another less-excited state). In this condition, known as population inversion, stimulated emission can occur, and the fiber can act as a laser or an optical amplifier. Thus, when a signal is injected into the fiber, the pump energy is transferred from the gain medium to the injected signal, thereby amplifying the injected signal as it propagates along the fiber.
Efforts have been made to alter the profile for the injected signal. However, what has not been extensively studied is the effect of shaping the pump.